1. Field of the Invention
The present invention relates to a light emitting apparatus and a method for driving the light emitting LED apparatus. The present invention also relates to a display apparatus including the light emitting apparatus.
2. Description of the Related Art
FIG. 20 illustrates a conventional LED driving apparatus. In the conventional LED driving apparatus, a driving current i corresponding to an output establishment value p is applied from a power source 191 to an LED device 192 to drive the LED device 192. The emission intensity of the LED device 192 is controlled by changing the value of the driving current i. In general, the color of light emitted from conventional LED devices does not depend on the value of a driving current. Thus, the emission intensity of conventional LED devices is changed by control of the driving current value while maintaining the color of light emitted from the LED devices.
The emission intensity of conventional LED devices can be solely changed by control of the driving current value, since the light color of the conventional LED devices is not affected by a change in the driving current value. However, there is another type of LED device having a light color which is altered by a change in the driving current value. When such an LED device is driven by a driving apparatus as shown in FIG. 20, the light color of the LED device is changed along with the emission intensity control thereof. Thus, a desired emission intensity control cannot be conducted.
Conventional AlGaAs semiconductor light emitting devices have a phenomenon in which the wavelength of light emitted therefrom becomes longer as a driving current is increased (red shift phenomenon). The red shift phenomenon occurs as follows. The light emitting device is heated by supplied power, and the temperature of the device is proportional to the average supplied power. The increased temperature causes the bandgap of the active layer to be reduced, so that the wavelength of light emitted from the device becomes longer (red shift). In other words, the emission intensity and emission wavelength of the light emitting device having the red shift phenomenon are determined by the average power applied to the device. It is not possible to separately control the emission wavelength and emission power of the AlGaAs semiconductor light emitting device using two parameters (peak value and average power) of a driving current pulse.